Very efficient, high temperature, silica-containing insulating materials exhibiting a thermal conductivity less than that of still air have been made commercially available. In the main, those products have resulted from powder technology developed for cryogenic and space applications. The forming process for such products has been a rather tedious one involving mixing finely-powdered, aerogel silica with radiation opacifier oxides, fiber reinforcement, and binder, and then pressing or slip casting the resultant mixture into a low density slab which is relatively weak. Thus, the forming process contemplates the handling problems inherent with low density powders and is ill-suited to fabricate bodies of intricate configurations.